全新java初学者实践教程6(Java SE5.0版)
l[Tt[n 基本语法3
R~$hWu}} M$F{N L7<+LA)s0 我们这个教程侧重的是实践的内容和语言的重点。在[font="Times]java语言中还有很多细节的东西,请参考[font="Times]sun公司的官方培训教程。我们这里不能一一讲述。这节课我们来给大家提供一些程序流程控制的一些例子供大家学习。计算机怎么做事情,是我们教给他的。我们用它解决实际生活中的问题,所以计算机要描述现实生活中的流程。[font="Times]Java语言中提供了[font="Times]4类程序控制语句,来描述流程:
e|JIrOnc @]E]W#xAn [font="Times] 1.循环语句[font="Times]:while,do-while,for
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w^7^q& aU4R+.M7@ [font="Times]2.分支语句[font="Times]:if-else,switch,
brj[c>ID [font="Times]
aj?2jU~Pq 3.跳转语句[font="Times] break,continue,label: 和[font="Times]return
8<Xq=*J+ [font="Times]
rykj2/O 4.异常处理语句[font="Times]:try-catch-finally,throw
8-A:k E aDN.gMS 实践:
X8i[fk1.R [font="Times] 1.循环语句
C/bxfp{? [font="Times] while 语句
PP],HB+*[ [font="Times]class While {
"~_$T@^k> [font="Times]public static void main(String args[]) {
sbgJw [font="Times]int n = 10;
"cNg: [font="Times]while(n > 0) {
WejyYqr34- [font="Times]System.out.println("tick " + n);
k~{Fnkt [font="Times]n--;
>n1h^AW [font="Times]}
We\KDU\n [font="Times]}
#jOOsfH|k [font="Times]}
dV)Y,Yx0${ [font="Times] do…while 语句
WFRsSp2 [font="Times] class DoWhile {
~m!#FTc* [font="Times]public static void main(String args[]) {
:MK:TJV [font="Times]int n = 10;
R9Ldl97' [font="Times]do {
#t){ 4J [font="Times]System.out.println("tick " + n);
)y(oHRCp-> [font="Times]n--;
xna7kA [font="Times]} while(n > 0);
^)Smv\Md [font="Times]}
1>hb-OMX [font="Times]}
hH#lTye 二者区别,[font="Times]do…while至少循环一次,而[font="Times]while的表达式要是为[font="Times]flase的话可以一次也不循环。再通俗一点,[font="Times]do…while就算是括号里的是[font="Times]flase,人家最少也能[font="Times]do一次。
pa>p% [font="Times] for语句
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"u [font="Times] class ForTick {
W8< @sq~I [font="Times]public static void main(String args[]) {
.#"1bRWpZ [font="Times]int n;
w<Zdq}{jO [font="Times]for(n=10; n>0; n--)
!X%S)VSMU [font="Times]System.out.println("tick " + n);
*3!(*F@M, [font="Times]}
X{#bJ [font="Times]}
7qpzk7X?pR 与上面那两个的区别,[font="Times]for循环执行的次数是可以在执行之前确定的。通俗一点说吧,看这个例子[font="Times] for(n=10; n>0; n--)就是在括号里的时候,就已经知道要循环[font="Times]10次了。
9z+vFk` 还有啊,[font="Times]for循环的部分可以为空的
0,:iE\ [font="Times]class ForVar {
JIVo=5c} [font="Times]public static void main(String args[]) {
+I*k0"gj6 [font="Times]int i;
h]<GTWj [font="Times]boolean done = false;
_cR6ik zW( [font="Times]i = 0;
eR7qE) h [font="Times]for( ; !done; ) {
?0 HR(N(z! [font="Times]System.out.println("i is " + i);
Pa3{Ds [font="Times]if(i == 10) done = true;
L7X7Zt8% [font="Times]i++;
0K&_D) [font="Times]}
ejP,29 [font="Times]}
>y]?MGk [font="Times]}
循环语句的例子下载 (qJIu [font="Times] 2.分支语句[font="Times]
9*BoYFw92* [font="Times] if/else语句
pi|\0lH6W [font="Times]class IfElse {
t#a.}Jl [font="Times]public static void main(String args[]) {
cZ6?P`X [font="Times]int month = 4; // April
b*cW<vX}~ [font="Times]String season;
:b.3CL\.6 [font="Times]if(month == 12 || month == 1 || month == 2)
a:=q8Qy [font="Times]season = "Winter";
$[)6H7!U) [font="Times]else if(month == 3 || month == 4 || month == 5)
|Uc<;> l [font="Times]season = "Spring";
X";TZk [font="Times]else if(month == 6 || month == 7 || month == 8)
_2wAaJvA [font="Times]season = "Summer";
tX@0:RX% [font="Times]else if(month == 9 || month == 10 || month == 11)
]^Sd9ba [font="Times]season = "Autumn";
th5
X?so [font="Times]else
C_6GOpl [font="Times]season = "Bogus Month";
5P-K *C& [font="Times]System.out.println("April is in the " + season + ".");
$Vo/CZW7 [font="Times]}
8FAT(f//. [font="Times]}
$$k7_rs [font="Times]//这段程序输出[font="Times]:
r5D jCV" [font="Times]//April is in the Spring.
<9=zP/Q [font="Times]// 注意[font="Times] “[font="Times]||”是或运算
Cw6>^ [font="Times] switch语句
n>u.3wL [font="Times] class Switch {
wYZy e^7 [font="Times]public static void main(String args[]) {
W/b"a? wE{ [font="Times]int month = 4;
s.f`.o [font="Times]String season;
d&/^34gn [font="Times]switch (month) {
>_rzT9gX& [font="Times]case 12:
` 52%XI [font="Times]case 1:
j kSc& [font="Times]case 2:
kTr6{9L [font="Times]season = "Winter";
-0{T [font="Times]break;
PthIdaN@ [font="Times]case 3:
`)0Rv|? [font="Times]case 4:
or?0PEx\ [font="Times]case 5:
{CW1t5$* [font="Times]season = "Spring";
0eQ~#~j& [font="Times]break;
_Syre6k [font="Times]case 6:
K%98;e9 [font="Times]case 7:
pGO|~:E/L [font="Times]case 8:
2 9&sydu [font="Times]season = "Summer";
^wvH,>Yo [font="Times]break;
Gtj( [font="Times]case 9:
CkmlqqUHC [font="Times]case 10:
xR\D(FLVS [font="Times]case 11:
z8
hTZU [font="Times]season = "Autumn";
99\{! W [font="Times]break;
|Dl*w/n
[font="Times]default:
%M|Z}2qv [font="Times]season = "Bogus Month";
$KoPGgC[ [font="Times]}
a Q.Iq [font="Times]System.out.println("April is in the " + season + ".");
LEYWH%y [font="Times]}
%1Vu=zCAW [font="Times]}
分支语句代码下载 v[0DE*p SQ1M4:hP [font="Times]switch语句适合于条件非常多的逻辑
+AE&GU 请看上述语句可以混合使用,请看
下载例子